While many parents grapple with an "empty nest" once their kids leave home, some enjoy the presence of their adult children for longer than expected. It's up to each family to gauge what works, and when it's best for kids to leave for good.

Storks rest in their nest on a chimney as temperatures rose up to 16 degrees Celsius (61 degrees Fahrenheit) on a sunny day in Naegelstedt, near Erfurt, central Germany, Monday, March 10.

Jens Meyer/Ap/FILE

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Research continues to confirm what many parents already know all too well, that adults are still living in their parents’ home in sizable numbers.

Gallup data released in February found that 14 percent of US adults ages 24-34 are living with parents, while 51 percent of those ages 18-23 were still living at home as well. All together, 29 percent of the under-35 population of the US are still living with parents.

This follows a 2013 Pew Research analysis of 2012 US Census Bureau data, which reported that 21.6 million "millennials" ages 18-31 were living at home with parents.

The reasons for this trend are many, but are often due to a transition for the young adults. Living costs are high, even if adult children share a space with a group, so they choose to spend some time back home and regroup before the next step. One commenter on a college blog described it as the only “responsible” choice.

My husband and I are among those readjusting to this situation. Our son decided it was a waste of money to continue attending a university out of the area. The local college is excellent and held the attraction of a track team he could join. So we, like many families, needed to negotiate the changes that must be made in a nest that had been adequately full with just the two of us.

Our son is good company, but it is another body coming and going, doing laundry, inviting friends in, and occasionally needing reminders. Unfortunately, he was not gone that long, so my mother mantra that goes, “Did you remember…?” is still operational. For us and for many families, it is necessary to redefine the relationship as one between “adults.”

Parents observe that kids seem to be maturing slower than they used to and that these returns home are part of that condition. A cartoon on a friend’s refrigerator echoed this with a picture of a father shouting at his son lounging on the sofa, “When I was your age, I was an adult!”

My husband often says, “60 is the new 40, but 22 is the new 16.” I sometimes wonder if we have abridged their actual childhoods so much that they linger in late adolescents to try to complete the process of growing up.

We can even find reasons in technology. With computers and cellphones, there is often constant contact between parents and their children. That could be having some impact on this indirect route to adulthood.

My friend Karen shared that sometimes the birds do not return by themselves. Her bird brought another with her. The 28-year-old daughter returned from a service project in Central America with her boyfriend. The luxury of staying with mom and dad allowed their daughter to hold out for the “right” job.

That arrangement was acceptable to Karen, but some parents expressed discomfort around the issue of having “romantic companions” spend the night. Perhaps less of a generation gap on this and other issues has made the situation more comfortable for both parents and children, but clarifying conditions prior to the move is critical.

Whether the reasons are economic, sociological, or technological, as the child in the movie “Poltergeist” once said, “They’re back.” So what do we do to make this new housing arrangement work?

After talking to several parents, some of the common issues that need to be negotiated are: different schedules, different standards of cleanliness, sharing of housekeeping chores, and a plan to eventually move out.

A colleague who survived the return advised, “Think ahead to what will make you crazy and make sure that it is a clearly stated condition.” The deal breaker for her was having a lot of the returnee’s possessions lying around in shared spaces. That issue was top of her list when she made arrangements with her “visiting” offspring.

The key in most successful situations has been a formal effort to create shared expectations. Parents have different priorities and pet peeves, but the consensus is to put them in writing and revisit them on a regular basis.

Defining a departure time for the re-nester helps some parents accept the situation with more grace. A plan to move out, even if it needs to be modified, is recommended. Some parents give their youngster a specific time after which point rent will be collected. Some parents collect from the beginning and save the money to eventually give to the youngster for first and last month’s rent in their own place.

Each family reported different concerns, and also shared some benefits. People had to give up guest rooms, sewing rooms, and exercise rooms that had been converted from their child’s room. They had to give up tidy spaces and a few nights of sleep with worries that linger when waiting for a “grown” child to come in at night. But most parents have become accustomed to the kids going out at about the same time they go to bed.

They have gained precious time with their young adult to share life lessons and to simply enjoy them. It was a little surprising to hear the positive things parents had to say about having their youngsters return. It was equally surprising to hear how grateful the youngsters were that the nest was still there to help them gain the strength they needed to fly away again.

The Christian Science Monitor has assembled a diverse group of the best family and parenting bloggers out there. Our contributing and guest bloggers are not employed or directed by the Monitor, and the views expressed are the bloggers' own, as is responsibility for the content of their blogs. Susan DeMersseman blogs at Raising kids, gardens and awareness.